Is the Fanning Friction Factor Calculation Affected by Unit Usage?

[gfd43tg]

Hello,

I was wondering if when calculating the fanning friction factor, do english units need to be used?

The equation for the head friction is

h_f = 4f(L/D)V^2/2

where L is the length, D is the diameter of the pipe, and f is the fanning friction factor. This ends up having units of length squared/time squared, but I think it should be power/mass

 

[SteamKing]

I don't know about your dimensional analysis. The Fanning friction factor is non-dimensional.

http://en.wikipedia.org/wiki/Fanning_friction_factor

BTW, your formula for head loss due to friction is incorrect. It should be:

h_f = 4f(L/D)V^2/(2g)

 

[gfd43tg]

Is the g included whether you use english units or not? I get confused when I need to divide by g or not these days since we keep going back and forth with english and SI units

 

[SteamKing]

Yes, the g is always there, even in SI or furlongs per fortnight units. Do a dimensional analysis and confirm.

 

[gfd43tg]

You can see why I was confused, this is directly and repeatedly on the lecture slides